ABSTRACT
In this chapter we discuss two important concepts in graph theory, namely, planarity and duality. First we consider planar graphs and derive some properties of these graphs. Characterizations of planar graphs due to Kuratowski, Wagner, Harary and Tutte, and to MacLane are also discussed. We then discuss Whitney’s definition of duality of graphs which is given in terms of circuits and cutsets and relate this concept to the seemingly unrelated concept of planarity.
